In the modern-day development of motor vehicles the development engineers strive to design as lightweight a motor vehicle as possible and, on account thereof, to reduce fuel consumption and environmental stress and to improve the handling of the vehicle on the road. The lightweight construction mode herein is, for example, implemented in that fiber-plastics composites are increasingly employed and, on account thereof, the weight of the motor vehicle is reduced by virtue of the density that is low in comparison to aluminum and in particular to steel.
A vehicle body is composed from a mixture of fiber-plastics composites and metallic body components, for example, wherein the fiber-plastics composites are connected to the metallic body components by screw or rivet connections, for example. Problematic in the case of such a hybrid lightweight construction of the vehicle body are the dissimilar thermal expansion behaviors of the various material groups. For example, problems arise in painting or in the subsequent drying procedure, respectively, which is performed at highest possible temperatures of 130° to 220°, for example, so as to complete the drying of the paintwork as rapidly as possible. On account of the dissimilar thermal expansion rates of the body components that arise in particular in the drying process, high mechanical stresses are created in the body components and in particular in the join connections, said mechanical stresses potentially leading to deformations and in the extreme to a breakage of the body component and/or of the join connections.
In order for the hybrid lightweight construction of the motor vehicle body from fiber-plastics composites and metallic body components to nevertheless be possible, it is known from the prior art for the fiber-plastics composites and the metallic body components in the non-assembled state to be painted separately and to be joined together thereafter. This variant leads to additional costs and increases the complexity of painting and assembling.
Another solution that is known from the prior art for avoiding stress loads by virtue of dissimilar thermal expansion behavior is to adapt the coefficient of thermal expansion of the fiber-plastics composite to the coefficient of thermal expansion of the metallic body component. EP 1 391 369 A2, for example, discloses a metallic body component and a body component that is embodied from a fiber-plastics composite, said components being interconnected by way of an adhesive connection. The fiber-plastics composite in the flange region herein is embodied in such a manner that the thermal expansion behavior of the fiber-plastics composite corresponds to the thermal expansion behavior of the metallic body component. The adaptation of the coefficient of thermal expansion of the fiber-plastics composite to the coefficient of thermal expansion of the metallic body component is performed by the orientation of the fibers that are embedded in a thermoplastic matrix, wherein the fibers in the flange region in relation to an orthogonal that is oriented so as to be perpendicular to the preferred direction of the flange region enclose an angle a=+/−10 to 30°.
It is disadvantageous in the case of the embodiment disclosed in EP 1 391 369 A2 that the fiber-plastics composite in the flange region, on account of the respective orientation of the fibers for adapting the coefficient of thermal expansion to the coefficient of thermal expansion of the metallic body component, leads to a reduction in the strength of the fiber-plastics composite.